The present invention is directed to a latching mechanism for a MEMS actuator and a method of fabrication.
Microelectromechanical systems (MEMS) have the potential to dramatically impact the fiber optic telecommunication industry (for example, in the control of switching mirrors used in Nxc3x97N matrix switches) and also for other functional elements such as variable attenuators and tunable filters. The scalability of micromachined elements makes MEMS the technology of choice for the above applications. For implementing the foregoing, electro-thermal in-plane actuators constructed using the MEMS technology are described in a paper entitled, xe2x80x9cBent Beam Electro-Thermal Actuators for High Force Applicationsxe2x80x9d by Long Que (a co-inventor of this application), et al. in a conference paper published in January of 1999 by the IEEE at the University of Wisconsin. This will be described below. Such actuators comprise a pair of beams meeting at an apex which upon application of a drive voltage expand to provide a rectilinear high force. Removal of the drive voltage of course returns the actuator to its original position. Thus, a necessary feature is a latch so the actuator will retain its position in the event of a power interruption. This allows the communication system to predict the state of the network during a power failure. In other words, a xe2x80x9cfail-safexe2x80x9d mode of operation is required.
It is therefore an object of the present invention to provide a latching mechanism for a MEMS actuator and a method of fabrication.
In accordance with the above object, there is provided a latching mechanism for a micro-electromechanical system (MEMS) actuator for applications including actuated devices in photonic switches, variable attenuators or tunable filters, including a thermal actuator having a pair of bent beams fabricated by the MEMS technique of semiconductive material for providing a beam junction, the beam junction having an actuator arm connected to the actuated device, the beam junction and arm having a rectilinear displacement motion for moving the actuated device by application of a drive voltage to the beams from a power supply, with the arm being moved from a non-actuated to an actuated position. A latching mechanism comprises latching means for maintaining the arm and actuated device in the actuated position even while a power supply interruption occurs, the latching means including at least a pair of clamps, actuated by bent beam actuators, juxtaposed on opposite sides of a portion of the arms. The clamps have a normally closed position in the absence of the drive voltage for stopping the arm motion and an open position upon an application of a drive voltage to the bent beams to allow the arm motion.